Continuously variable transmission and control method thereof

Abstract

The transmission controller performs a non-coordinated shift, in which the gear position of the subtransmission mechanism is modified from the second gear position to the first gear position at a higher speed than when the gear position of the subtransmission mechanism is modified by a coordinated shift while permitting a deviation between the through speed ratio and the target through speed ratio, instead of the coordinated shift when it is determined that the second speed kick down shift is to be performed.

1. A continuously variable transmission installed in a vehicle, comprising:
 a variator capable of varying a speed ratio continuously; 
 a subtransmission mechanism provided in series with the variator and having a first gear position and a second gear position as forward gear positions, the second gear position having a smaller speed ratio than the first gear position; 
 a destination through speed ratio setting unit which sets, on the basis of an operating condition of the vehicle, a destination through speed ratio, which is a target value to be reached by a through speed ratio serving as an overall speed ratio of the variator and the subtransmission mechanism in accordance with the operating condition; 
 a target through speed ratio setting unit which sets, on the basis of the destination through speed ratio, a target through speed ratio serving as a transitional target value for making the through speed ratio to follow the destination through speed ratio at a predetermined transient response; 
 a shift control unit which controls at least one of the variator and the subtransmission mechanism such that the through speed ratio follows the target through speed ratio; 
 a coordinated shifting unit which performs a coordinated shift, in which the speed ratio of the subtransmission mechanism is varied while varying the speed ratio of the variator in an opposite direction to a speed ratio variation direction of the subtransmission mechanism so that the through speed ratio reaches the target through speed ratio, when modifying a gear position of the subtransmission mechanism; 
 a second speed kick down shift determining unit which determines that a second speed kick down shift accompanied by modification of the gear position of the subtransmission mechanism from the second gear position to the first gear position is to be performed due to depression of an accelerator pedal; and 
 a non-coordinated shifting unit which performs a non-coordinated shift, in which the gear position of the subtransmission mechanism is modified from the second gear position to the first gear position at a higher speed than when the gear position of the subtransmission mechanism is modified by the coordinated shift while permitting a deviation between the through speed ratio and the target through speed ratio, instead of the coordinated shift performed by the coordinated shifting unit when the second speed kick down shift determining unit determines that the second speed kick down shift is to be performed. 
 
     
     
       2. The continuously variable transmission as defined in  claim 1 , further comprising a variator shift suppressing unit which suppresses variation in a speed ratio of the variator during the non-coordinated shift. 
     
     
       3. The continuously variable transmission as defined in  claim 1 , further comprising a overshoot determining unit which determines whether or not an overshoot, in which an input rotation speed of the continuously variable transmission increases beyond an input rotation speed of the continuously variable transmission obtained when the through speed ratio is varied to the destination through speed ratio by at least a predetermined increase width, will occur as a result of the non-coordinated shift,
 wherein, when the overshoot determining unit determines that the overshoot will occur, the non-coordinated shifting unit does not perform the non-coordinated shift even if the second speed kick down shift determining unit determines that the second speed kick down shift is to be performed, and instead, the coordinated shifting unit performs the coordinated shift. 
 
     
     
       4. The continuously variable transmission as defined in  claim 1 , further comprising an over-revving determining unit which determines whether or not over-revving, in which the input rotation speed of the continuously variable transmission exceeds a predetermined upper limit value, will occur as a result of the non-coordinated shift,
 wherein, when the over-revving determining unit determines that the over-revving will occur, the non-coordinated shifting unit does not perform the non-coordinated shift even if the second speed kick down shift determining unit determines that the second speed kick down shift is to be performed, and instead, the coordinated shifting unit performs the coordinated shift. 
 
     
     
       5. A control method for a continuously variable transmission which is installed in a vehicle and includes a variator capable of varying a speed ratio continuously, and a subtransmission mechanism provided in series with the variator and having a first gear position and a second gear position as forward gear positions, the second gear position having a smaller speed ratio than the first gear position, the control method comprising:
 setting, on the basis of an operating condition of the vehicle, a destination through speed ratio, which is a target value to be reached by a through speed ratio serving as an overall speed ratio of the variator and the subtransmission mechanism in accordance with the operating condition; 
 setting, on the basis of the destination through speed ratio, a target through speed ratio serving as a transitional target value for making the through speed ratio to follow the destination through speed ratio at a predetermined transient response; 
 controlling at least one of the variator and the subtransmission mechanism such that the through speed ratio follows the target through speed ratio; 
 performing a coordinated shift, in which the speed ratio of the subtransmission mechanism is varied while varying the speed ratio of the variator in an opposite direction to a speed ratio variation direction of the subtransmission mechanism so that the through speed ratio reaches the target through speed ratio, when modifying a gear position of the subtransmission mechanism; 
 determining that a second speed kick down shift accompanied by modification of the gear position of the subtransmission mechanism from the second gear position to the first gear position is to be performed due to depression of an accelerator pedal; and 
 performing a non-coordinated shift, in which the gear position of the subtransmission mechanism is modified from the second gear position to the first gear position at a higher speed than when the gear position of the subtransmission mechanism is modified by the coordinated shift while permitting a deviation between the through speed ratio and the target through speed ratio, instead of the coordinated shift when it is determined that the second speed kick down shift is to be performed. 
 
     
     
       6. The control method as defined in  claim 5 , further comprising suppressing variation in a speed ratio of the variator during the non-coordinated shift. 
     
     
       7. The control method as defined in  claim 5 , further comprising determining whether or not an overshoot, in which an input rotation speed of the continuously variable transmission increases beyond an input rotation speed of the continuously variable transmission obtained when the through speed ratio is varied to the destination through speed ratio by at least a predetermined increase width, will occur as a result of the non-coordinated shift,
 wherein, when it is determined that the overshoot will occur, the non-coordinated shift is not performed even if it is determined that the second speed kick down shift is to be performed, and instead, the coordinated shift is performed. 
 
     
     
       8. The control method as defined in  claim 5 , further comprising determining whether or not over-revving, in which the input rotation speed of the continuously variable transmission exceeds a predetermined upper limit value, will occur as a result of the non-coordinated shift,
 wherein, when it is determined that the over-revving will occur, the non-coordinated shift is not performed even if it is determined that the second speed kick down shift is to be performed, and instead, the coordinated shift is performed. 
 
     
     
       9. A continuously variable transmission installed in a vehicle, comprising:
 a variator capable of varying a speed ratio continuously; 
 a subtransmission mechanism provided in series with the variator and having a first gear position and a second gear position as forward gear positions, the second gear position having a smaller speed ratio than the first gear position; 
 destination through speed ratio setting means for setting, on the basis of an operating condition of the vehicle, a destination through speed ratio, which is a target value to be reached by a through speed ratio serving as an overall speed ratio of the variator and the subtransmission mechanism in accordance with the operating condition; 
 target through speed ratio setting means for setting, on the basis of the destination through speed ratio, a target through speed ratio serving as a transitional target value for making the through speed ratio to follow the destination through speed ratio at a predetermined transient response; 
 shift control means for controlling at least one of the variator and the subtransmission mechanism such that the through speed ratio follows the target through speed ratio; 
 coordinated shifting means for performing a coordinated shift, in which the speed ratio of the subtransmission mechanism is varied while varying the speed ratio of the variator in an opposite direction to a speed ratio variation direction of the subtransmission mechanism so that the through speed ratio reaches the target through speed ratio, when modifying a gear position of the subtransmission mechanism; 
 second speed kick down shift determining means for determining that a second speed kick down shift accompanied by modification of the gear position of the subtransmission mechanism from the second gear position to the first gear position is to be performed due to depression of an accelerator pedal; and 
 non-coordinated shifting means for performing a non-coordinated shift, in which the gear position of the subtransmission mechanism is modified from the second gear position to the first gear position at a higher speed than when the gear position of the subtransmission mechanism is modified by the coordinated shift while permitting a deviation between the through speed ratio and the target through speed ratio, instead of the coordinated shift performed by the coordinated shifting means when the second speed kick down shift determining means determines that the second speed kick down shift is to be performed. 
 
     
     
       10. The continuously variable transmission as defined in  claim 9 , further comprising variator shift suppressing means for suppressing variation in a speed ratio of the variator during the non-coordinated shift. 
     
     
       11. The continuously variable transmission as defined in  claim 9 , further comprising overshoot determining means for determining whether or not an overshoot, in which an input rotation speed of the continuously variable transmission increases beyond an input rotation speed of the continuously variable transmission obtained when the through speed ratio is varied to the destination through speed ratio by at least a predetermined increase width, will occur as a result of the non-coordinated shift,
 wherein, when the overshoot determining means determines that the overshoot will occur, the non-coordinated shifting means does not perform the non-coordinated shift even if the second speed kick down shift determining means determines that the second speed kick down shift is to be performed, and instead, the coordinated shifting means performs the coordinated shift. 
 
     
     
       12. The continuously variable transmission as defined in  claim 9 , further comprising over-revving determining means for determining whether or not over-revving, in which the input rotation speed of the continuously variable transmission exceeds a predetermined upper limit value, will occur as a result of the non-coordinated shift,
 wherein, when the over-revving determining means determines that the over-revving will occur, the non-coordinated shifting means does not perform the non-coordinated shift even if the second speed kick down shift determining means determines that the second speed kick down shift is to be performed, and instead, the coordinated shifting means performs the coordinated shift. 
 
     
     
       13. A continuously variable transmission for a vehicle, comprising:
 a variator capable of varying a speed ratio continuously; 
 a subtransmission mechanism provided in series with the variator and having a first gear position and a second gear position as forward gear positions, the second gear position having a smaller speed ratio than the first gear position; 
 a coordinated shifting unit which performs a coordinated shift, in which a shift speed of the subtransmission is made identical to a shift speed of the variator, and the speed ratio of the variator is varied in an opposite direction to a speed ratio variation direction of the subtransmission mechanism while the subtransmission is shifted, when modifying a gear position of the subtransmission mechanism; and 
 a non-coordinated shifting unit which performs a non-coordinated shift, in which the coordinated shift is stopped and the shift speed of the subtransmission is made faster than the shift speed during the coordinated shift when there is a kick-down request from a driver and a downshift of the subtransmission is possible. 
 
     
     
       14. The continuously variable transmission as defined in  claim 13 , further comprising a variator shift suppressing unit which suppresses variation in a speed ratio of the variator during the non-coordinated shift. 
     
     
       15. The continuously variable transmission as defined in  claim 13 , further comprising:
 a destination through speed ratio setting unit which sets, on the basis of an operating condition of the vehicle, a destination through speed ratio, which is a target value to be reached by a through speed ratio serving as an overall speed ratio of the variator and the subtransmission mechanism in accordance with the operating condition; and 
 an overshoot determining unit which determines whether or not an overshoot, in which an input rotation speed of the continuously variable transmission increases beyond an input rotation speed of the continuously variable transmission obtained when the destination through speed ratio is varied to a target value to be reached by at least a predetermined increase width, will occur as a result of the non-coordinated shift, 
 wherein, when the overshoot determining unit determines that the overshoot will occur, the non-coordinated shifting unit does not perform the non-coordinated shift even if there is the kick-down request and the downshift of the subtransmission is possible, and instead, the coordinated shifting unit performs the coordinated shift. 
 
     
     
       16. The continuously variable transmission as defined in  claim 13 , further comprising an over-revving determining unit which determines whether or not over-revving, in which the input rotation speed of the continuously variable transmission exceeds a predetermined upper limit value, will occur as a result of the non-coordinated shift,
 wherein, when the over-revving determining unit determines that the over-revving will occur, the non-coordinated shifting unit does not perform the non-coordinated shift even if there is the kick-down request and the downshift of the subtransmission is possible, and instead, the coordinated shifting unit performs the coordinated shift.